1. The Field of the Invention
The present invention relates to systems, apparatus and methods for testing optical transceivers. More particularly, the present invention relates to apparatus and methods for testing small form factor optical transceivers with optical components that are an integral part of the optical transceivers.
2. Background and Relevant Art
Fiber optic networks often include a transmission side and a receiver side. On the transmission side, it is important that the light be efficiently coupled into the transmission fiber in order to achieve adequate transmission power with minimum laser output strength. On the receiver side, it is important to efficiently image the fiber output onto detectors with adequate margin for error. This is particularly true as the size of detectors decreases, often for cost reasons.
Effective coupling of the light into the optical fiber on the transmission side and effective coupling of the optical fiber output to a detector is often achieved through the use of small form factor optical transceivers or miniature ports that house small optical elements. These optical transceivers or ports are highly desirable because they are small. In addition, these optical transceivers incorporate or integrate two or more optical components into a common assembly. The common assembly, especially when the coupling or lens element is simply molded as an integral part of the port, simplifies manufacturing processes and reduces cost. Further cost reduction can also be achieved by molding the coupling lens and the mechanical port as a single unit.
The lens or coupling elements of the optical transceivers are often pressed or glued within the optical transceiver or are molded as an integral part of the transceiver. In spite of the advantages afforded by these small the small size and the embedded position of the optical components, the size of the optical transceiver can also present several problems. The optical quality of the lens that is embedded in the port of the optical transceiver, for instance, is dependent on the surface accuracy, surface and volume material quality, and positional accuracy of the lens with respect to the body of the port.
Deviations of the surface curvature of the integrated lens from the design curvature of the integrated lens, due to the molding process or pressing of the molded lens element into the housing of the optical transceiver, can introduce errors and aberrations into an optical system. Other surface and volume degradations such as scratches, digs, and bubbles introduced in the molding process or as a result of placement and fixing of the molded lens element inside the port also reduce the optical efficiency of the coupling element in an optical system. The combined effect of these and other errors lessen the overall quality of a particular optical transceiver.
These types of errors are usually detected or measured using interferometric optical surface measurements. A mechanical profiler, for example, may be used to detect some of these errors. In small form factor optical transceivers, however, it is difficult and cumbersome to use standard optical equipment to perform the usual optical surface measurements because of the small geometry of the optical transceiver. In particular, the embedded nature of the lens in the optical transceiver makes a traditional analysis of the lens element impractical and costly.